An acceleration sensor includes a seismic mass which is suspended on springs above a substrate, and is deflectable in a direction perpendicular to a surface of the substrate.
The deflection of the seismic mass in a direction perpendicular to the substrate because of an acceleration is detected by an electrode provided below the seismic mass on the substrate. Due to interference accelerations, the seismic mass is able to be deflected not only in a direction perpendicular to the surface of the substrate, but also along the surface of the substrate. Because of inaccuracies when manufacturing the springs, an interference acceleration along the surface of the substrate can also lead to a deflection perpendicular to the substrate surface, the measurement of the acceleration perpendicular to the surface of the substrate thereby being falsified. Especially because of vibrations, the seismic mass of the acceleration sensor can be induced to oscillate with a natural frequency along the surface of the substrate, these oscillations then falsifying the measurement of the acceleration perpendicular to the surface of the substrate. In this context, the natural frequency of the oscillations along the surface of the substrate is a function of the stiffness of the springs along the surface of the substrate.
In each case, the springs are made of an elongated, flexible element. The stiffness of the springs along the surface of the substrate can be increased by enlarging the cross-section of the flexible elements. However, the stiffness of the springs perpendicular to the surface of the substrate thereby increases at the same time. The sensitivity of the acceleration sensor to deflections in the z-direction decreases correspondingly.